Blood in the Nappy: A Five-Month-Old with Faltering Growth
A five-month-old Kuwaiti girl is brought to the paediatric clinic by her mother. She was exclusively breastfed until four months, when a standard cow's milk-based infant formula was introduced because the mother returned to work. Over the following five weeks she developed loose stools containing mucus and visible streaks of blood, perianal excoriation, worsening facial eczema and occasional non-bilious vomiting. She now takes about 150 mL of formula six times a day. Birth weight was 3.2 kg; she tracked the 50th centile until four months and now weighs 5.4 kg, below the 3rd centile, with length 62 cm. She is afebrile, alert and not dehydrated. Haemoglobin 10.8 g/dL, eosinophils 700/microlitre, albumin 38 g/L, total IgE within the reference range. The mother asks for a soy formula because it is cheaper and available at the local pharmacy.
1. What is the most likely diagnosis, how does the history support it, and what diagnostic step would you take rather than ordering allergy tests?
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The picture is cow's milk protein allergy (CMPA), most likely the non-IgE-mediated or mixed type: symptoms began within weeks of introducing a cow's milk formula, and consist of bloody-mucoid stools, perianal excoriation, vomiting and eczema with faltering growth. The normal total IgE and modest eosinophilia do not exclude it - roughly 60% of CMPA is non-IgE-mediated.
The timing is the strongest discriminator. Symptoms appearing days to weeks after the formula started, without urticaria, angioedema, wheeze or acute collapse, point away from IgE-mediated disease and away from lactose intolerance, which causes watery acidic stools, nappy rash and gas but never visible blood or mucus. Infective colitis is less likely in an afebrile, thriving-until-recently infant with a five-week history.
The correct diagnostic step is a trial of elimination: a strict cow's milk protein-free diet for 2-4 weeks with symptom and growth monitoring. If symptoms resolve, the diagnosis is confirmed by supervised rechallenge, ideally in hospital for a non-IgE presentation with growth faltering. Skin prick tests and specific IgE are useful only for IgE-mediated disease and would here generate false reassurance or unnecessary dietary restriction.
2. Write the feeding plan. Address the mother's request for soy formula and calculate the volume and expected energy intake.
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Soy formula is the wrong choice here. Around 10-15% of infants with CMPA react to soy protein, soy infant formula is not recommended under six months in current paediatric guidance, and the blood and mucus indicate a protein-driven colitis rather than a carbohydrate problem. Rice drinks are also unacceptable - they are not infant formula and provide inadequate protein and energy.
The first-line choice is an extensively hydrolysed formula (eHF), which roughly 90% of infants tolerate. If there were severe symptoms, anaphylaxis, or failure to improve on eHF, an amino-acid formula would be indicated. Required volume is 150-180 mL/kg/day; at 5.4 kg that is 810-970 mL/day of a 67 kcal/100 mL formula, giving about 540-650 kcal/day, divided into 5-6 feeds of 150-180 mL. Currently she takes only 900 mL but her growth suggests intake is not the whole story - the colitis is causing losses and poor absorption.
If the mother wishes to resume breastfeeding, she must eliminate all cow's milk protein from her own diet for at least 2-4 weeks, including hidden sources such as ghee, laban, cheese and baked goods, while taking 1,000 mg calcium and vitamin D daily. A dietitian review of her intake is essential, and she needs written lists of permitted Kuwaiti foods in Arabic.
3. Set out your follow-up plan and the criteria that would make you change course or refer.
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Review at 2 weeks and 4 weeks with a weight, length and head circumference plotted on the same WHO chart. Expected response is resolution of blood and mucus within 2-4 weeks and a weight gain of roughly 20-30 g/day in a five-month-old during catch-up; anything less than 15 g/day at the 4-week review is a failure to respond and demands action, not more waiting.
At each visit check: stool blood and mucus, eczema severity, vomiting, feed volume taken, and whether the family can actually afford and access the eHF - cost and pharmacy stock are genuine barriers in Kuwait and a prescription that the family cannot fill is a failed plan. Provide the mother with a written emergency plan and a letter for the nursery stating the diagnosis and the foods to avoid.
Refer to paediatric gastroenterology if there is persistent blood or anaemia (haemoglobin was already 10.8 g/dL), if weight falls further or does not improve on eHF after 4 weeks, if hypoalbuminaemia or oedema develops, or if an amino-acid formula is needed. Also refer if the family needs support with the cost of the formula or with maternal elimination diet adherence.